Agriculture Reference
In-Depth Information
to adjust fl ow rate and fi neness of spray are
an alternative to using watering cans. Care is
needed because poor adjustment of fl ow can
lead to damage to soil, growing media and plants
especially if a powerful jet of water is selected.
X
Sprinklers
become an obvious choice, when
allowed, to deliver water to a large area rather
than to individual plants or containers. Bare
soils are vulnerable to droplet damage. Large
and fast-moving droplets damage soil crumbs in
seedbeds as well as disturbing seeds. Standing
water develops when the delivery rate exceeds
infi ltration rates; standing water leads to soil cap
formation (see p. 150). On slopes, run-off can
cause erosion of soil and even losses of seeds and
fertilizer. There is high water loss by evaporation
associated with water in the air and on soil
surfaces. It also creates a humid atmosphere.
X
Trickle lines
or
seep hoses
(Figure 12.16)
deliver water very slowly to the soil, leaving plant
foliage and most of the soil surface dry, which
ensures a drier atmosphere and reduced water
loss. However, care is needed because there is
very little sideways spread of water into coarse
sand, loose soil or a growing medium that has
completely dried out.
X
Drip irrigation
is a variation on the trickle method,
but the water is applied through pegged-down
thin, fl exible 'spaghetti' tubes to exactly where it
is needed - for example, the base of each plant
(see Figure 15.6b). This minimizes water loss
because no water is put in the air and only a small
proportion of the growing media surface is wetted.
X
Minimize evaporation of water
. This is best
achieved by not spraying water into the air and by
minimizing the time when the soil surface is moist.
When water does have to be applied overhead, this
should be undertaken in cool periods of the day.
X
Increase the water reservoir of the soil
. The
application of water can be reduced by increasing
the available water for the plants; by increasing
rooting depth, adding organic matter and/or adding
water-holding gel supplements to composts.
X
Improve soil structure
.
Help roots explore the
maximum amount of soil. Compacted layers in
the soil (soil pans) should be eliminated and good
soil structure maintained to increase the effective
rooting depth.
X
Plant root system
. Plants should be encouraged
to establish as quickly as possible but, after the
initial watering-in, infrequent applications will
encourage the plant to put down deeper roots by
searching for water.
X
Minimize water lost through drainage
. This
is not only to avoid losses of water from the
root zone but also the associated leaching of
soluble nutrients. Adding water to an outdoor soil
(irrigation) should be to fi eld capacity and no more.
Avoid adding the full soil moisture defi cit when rain
is imminent.
Further reading
Ashman, M.R. and Puri, G. (2002)
Essential Soil
Science.
Blackwell Science.
Bell, B. and Cousins, S. (1997)
Machinery for
Horticulture.
2nd edn
.
Old Pond Publishing.
Culpin, C. (1992)
Farm Machinery.
2nd edn
.
Blackwell
Science.
Davies D.G., Eagle D.T. and Finley J.B. (1993)
Soil
Management
.
5th edn. Farming Press Books and
Videos.
Ellis, S. and Mellor, A. (1995)
Soils and Environment
.
Routledge.
Ingram, D.S. et al. (eds) (2008)
Science and the
Garden.
2nd edn. Blackwell Science.
McIntyre, K. and Jakobsen, B. (1998)
Drainage for
Sportsturf and Horticulture.
Horticultural Engineering
Consultancy.
Munns, D.N. and Singer, M.J. (2005)
Soils: An
Introduction.
6th
edn.
Prentice Hall.
Prentice Baily, R. (1990)
Irrigated Crops and Their
Management.
Farming Press.
Water conservation
The need to manage water efficiently is a major
concern in the use of scarce resources. Responsible
action is increasingly supported by legislation and
encouraged by the higher price of using water. The
major factors that determine the level of water use are
related to the choice of plant species and the reasons
for growing. There are many ways by which water use
can be reduced if certain principles are kept in mind
and acted upon appropriately:
X
Plant selection
.
Choose drought-tolerant rather
than water-intensive plantings.
X
Use recycled water
. Whenever possible, the use
of mains water should be avoided. The capture
of rainwater is an important consideration in the
choice of water source.
Please visit the companion website for further information:
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